Communication pubs.acs.org/jchemeduc
An Easily-Assembled Soxhlet Extractor to Demonstrate Continuous Extraction Kevin M. Jones,* Iain A. Smellie,* and Iain L. J. Patterson School of Chemistry, University of St Andrews, St Andrews KY16 9ST, United Kingdom S Supporting Information *
ABSTRACT: The construction of a Soxhlet extractor from readily available laboratory equipment is described. The apparatus can be used to demonstrate the concept of continuous extraction and was used in the isolation of trimyristin from nutmeg.
KEYWORDS: High School/Introductory Chemistry, First-Year Undergraduate/General, Analytical Chemistry, Hands-On Learning/Manipulatives
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INTRODUCTION The Soxhlet extractor is a classic piece of chemical apparatus1,2 that is used to extract sparingly soluble material from a solid sample. Several experiments based on this concept have been published in this Journal, including the isolation of caffeine from beverage plants3 and piperine from black pepper.4 Soxhlet extractors are intricate pieces of glassware, making them both fragile and relatively expensive. The cost of such equipment can be restrictive, especially for schools and universities with limited budgets.5 In this paper we describe the construction of a Soxhlet extractor from readily available equipment and demonstrate its use in the extraction of trimyristin from nutmeg.6
to the following procedure: Ground nutmeg (3 g) was placed in a thimble made from a folded filter paper and inserted into the Soxhlet chamber, followed by a glass vial containing ice/water.8 Dichloromethane (70 mL) was added to the two-neck flask, followed by three or four boiling chips. The flask was heated to reflux and allowed to operate for 1 h. The coolant within the condenser was periodically replaced with a syringe/pipet to maintain a temperature capable of condensing the solvent vapor. After 1 h the reaction vessel was removed from the heat and allowed to cool to room temperature. The boiling chips were removed by filtration, and the resulting solution was reduced to dryness on a rotary evaporator to afford a yellow oil that solidified on cooling (1.2 g). The yellow solid was recrystallized from ethanol to afford a white solid (0.12 g, 4% yield based on the mass of nutmeg, mp 53 °C). Full details can be found in the Supporting Information.
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AN EASILY-ASSEMBLED VARIANT Our variant of the Soxhlet extractor is shown in Figure 1. The Soxhlet chamber is constructed from a 50 mL syringe barrel, a glass vial filled with an appropriate coolant to act as a condenser, and a siphon made from a length of tubing that serves to periodically empty the cavity, allowing the solid to be extracted with fresh solvent. The material to be extracted is placed in a folded filter paper and inserted into the chamber. The extraction chamber is connected to a two-neck flask with a length of wide-diameter plastic tubing and a 1 mL syringe barrel. Full details on how to construct the Soxhlet extractor and cross-sectional line drawings of a traditional all-glass Soxhlet extractor compared with our easily assembled variant can be found in the Supporting Information.
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SAFETY RECOMMENDATIONS Although in principle alternative solvents could be used in this version of the Soxhlet extractor, the authors strongly recommend that dichloromethane be used as the extraction solvent. Dichloromethane is nonflammable and has a low boiling point, making it an ideal solvent for this demonstration.
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EXPERIMENT TESTING Next, we wished to determine whether our protocol could be reproduced in students’ hands. Twenty undergraduate students carried out this experiment as part of an extracurricular lab
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EXPERIMENTAL SECTION To demonstrate the effectiveness of our apparatus, we examined the extraction of trimyristin7 from nutmeg according © XXXX American Chemical Society and Division of Chemical Education, Inc.
Received: December 14, 2016 Revised: March 26, 2017
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DOI: 10.1021/acs.jchemed.6b00965 J. Chem. Educ. XXXX, XXX, XXX−XXX
Journal of Chemical Education
Communication
concept of continuous extraction to a wider range of students, especially younger students in a school environment.
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ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available on the ACS Publications website at DOI: 10.1021/acs.jchemed.6b00965. Parts list, instructions for making the Soxhlet extractor, a figure comparing the traditional and easily assembled variants, and experimental details for the extraction and purification of trimyristin (PDF, DOCX) Video demonstrating the construction and operation of the Soxhlet extractor (AVI)
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AUTHOR INFORMATION
Corresponding Authors
*E-mail:
[email protected]. *E-mail:
[email protected]. ORCID
Kevin M. Jones: 0000-0002-2933-8553 Iain A. Smellie: 0000-0002-5829-6487 Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS We thank the Engineering and Physical Sciences Research Council, University of St Andrews, and the CRITICAT Centre for Doctoral Training for financial support [Grant EP/ 120L016419/1]. We also thank students enrolled on the CRITICAT programme for their help in testing the experiment.
Figure 1. Assembled Soxhlet extractor consisting of a two-neck flask, a syringe Soxhlet chamber containing the material to be extracted, a glass vial containing ice to act as a condenser, and plastic tubing to serve as a siphon.
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course. Each student was provided with both written and video instructions, and we were delighted to find that they were able to accurately reproduce the experiment with limited assistance. Students also provided feedback on minor problems they had encountered and how the instructions could be amended to circumvent these issues. As an example, several students used a particularly long piece of tubing to connect the round-bottom flask to the Soxhlet chamber. This was found to introduce dips in the tubing in which solvent could collect, hindering vapor reaching the Soxhlet chamber. This could be avoided by ensuring that the tubing between the two vessels is as short as possible. A series of “construction tips” were added to the instructions to make users aware of these potential problems.
REFERENCES
(1) Jensen, W. B. The Origin of the Soxhlet Extractor. J. Chem. Educ. 2007, 84 (12), 1913−1914. (2) Royal Society of Chemistry. Chemistry World: Classic KitThe Soxhlet Extractor. http://www.rsc.org/chemistryworld/Issues/2007/ September/ClassicKitSoxhletExtractor.asp (accessed March 25, 2017). (3) Adam, D. J.; Mainwaring, J.; Quigley, M. N. Soxhlet Extraction of Caffeine from Beverage Plants. J. Chem. Educ. 1996, 73 (12), 1171. (4) Epstein, W. W.; Netz, D. F.; Seidel, J. L. Isolation of Piperine from Black Pepper. J. Chem. Educ. 1993, 70 (7), 598−599. (5) Wesolowski, S. S.; Mulcahy, T.; Zafoni, C. M.; Wesolowski, W. E. The Development of a Microscale Continuous Hot Solvent Extractor. J. Chem. Educ. 1999, 76 (8), 1116−1117. (6) Frank, F.; Roberts, T.; Snell, J.; Yates, C.; Collins, J. Trimyristin from Nutmeg. J. Chem. Educ. 1971, 48 (4), 255−256. (7) Although the easily assembled Soxhlet extractor described can in principle be used for alternative extractions (e.g., the isolation of cinnamaldehyde from cinnamon), the authors recommend the isolation of trimyristin because the product can be easily purified by recrystallization, making it ideal for demonstrating the concept of continuous extraction. (8) Other coolant mixtures such as salt/ice and dry ice/acetone can also be used.
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HAZARDS Safety glasses, lab coats, and gloves should be worn during all experimental work. The experiment should be fully riskassessed before any practical work is undertaken. All experimental work should be carried out in a well-ventilated fume hood. All compounds should be treated as potentially hazardous. Dichloromethane can cause skin and serious eye irritation and may cause respiratory irritation and damage to organs. Ethanol is flammable and may cause irritation through contact or inhalation.
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CONCLUSION An easily constructed Soxhlet extractor has been developed and tested through the extraction of trimyristin from nutmeg. Our hope is that this apparatus can be used to demonstrate the B
DOI: 10.1021/acs.jchemed.6b00965 J. Chem. Educ. XXXX, XXX, XXX−XXX
